Project Summary Initiated in 2003, the goal of The 90+Study is to perform prospective clinical, pathological, and genetic investigations in a population based sample of people aged 90 years and older. With a wealth of cognitive tests, laboratory studies, physical performance measures, genetic and other data in The 90+ Study, plus survey information collected on these individuals since 1981 as part of the Leisure World Cohort Study, we will estimate incidence rates and evaluate risk and protective factors for dementia (Aim 1), functional disability and frailty (Aim 2), as well as cognitive and functional decline in the oldest old (Aim 3). Our studies emphasize potentially modifiable factors (oxygen saturation, anemia, and physical performance) as risk factors for dementia and disability in this age group, and could potentially provide the basis for future intervention studies in the oldest old. Based on our preliminary studies, we hypothesize that poor arterial oxygen saturation is a risk factor for cognitive decline and dementia, while anemia and physical performance measures (such as walk speed and handgrip) are risk factors for the development of disability, frailty, and functional decline in demented and non demented individuals. Half of all demented subjects in this age range do not have significant classical AD or other pathologies to explain cognitive loss. In this application, new collaborations enhance our clinical pathological studies investigating the biological correlates of cognition in the oldest old (Aim 4). Brain tissues from our well characterized subjects will be studied by investigators at the University of California, Irvine, University of Pennsylvania, and Johns Hopkins School of Medicine as we test our hypotheses that soluble, rather than insoluble, oligomeric species of A2, tau and 1 synuclein may be responsible for cognitive loss in 90+ year olds (Aim 4b) and that non AD pathologies, relevant to neuronal integrity and circuits, may contribute to cognitive loss through other age related mechanisms (Aim 4c). Finally, we will develop our clinical data and biological samples (brain tissues and DNA) as a resource to be actively shared with scientists worldwide. Project Narrative Understanding factors that influence the cognitive and functional status of the most senior members of our society is a major goal of this proposal. In our prospective studies of dementia, disability, and frailty in the oldest old, we will investigate the relationship to dementia, disability, and frailty of arterial O2 saturation, anemia, physical performance measures, and other factors that might be amenable to intervention. Ultimately our goal is to find ways to extend life without disability in nonagenarians and centenarians. If low O2 saturation, anemia or poor physical performance is associated with increased risk of dementia or disability in exceptionally long life, it would provide the basis for experimental studies to determine if oxygen therapy, treatment of anemia, or exercise could prevent or delay the loss of cognition and activities of daily living in the oldest old. The potential public health implications are enormous for the fastest growing segment of our population.